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Title:Mikrostrukturiranje in razločevanje naprednih optičnovlakenskih senzorskih struktur : doktorska disertacije
Authors:ID Javornik, Jure (Author)
ID Đonlagić, Denis (Mentor) More about this mentor... New window
Files:.pdf DOK_Javornik_Jure_2026.pdf (11,47 MB)
MD5: 5DC31EF4186F5E3D6C5007B577F4917E
 
Language:Slovenian
Work type:Doctoral dissertation
Typology:2.08 - Doctoral Dissertation
Organization:FERI - Faculty of Electrical Engineering and Computer Science
Abstract:Področje optičnovlakenskih senzorjev je v zadnjih desetletjih doživelo znaten razvoj, saj ti omogočajo meritve fizikalnih in kemičnih veličin z visoko ločljivostjo in občutljivostjo ter hkrati ponujajo edinstvene lastnosti, kot so odpornost na elektromagnetne motnje, zmožnost delovanja v zahtevnih okoljih, električno pasivna zgradba in možnost enostavne implementacije porazdeljenih merilnih shem. Kljub vsem prednostim je njihova uporaba v širšem naboru aplikacij omejena s kompleksnostjo in cenovno neugodnostjo sistemov za njihovo branje oziroma razločevanje kot tudi z zahtevnostjo senzorskih struktur samih. Predstavljeni omejitvi, ki preprečujeta širšo uporabo optičnovlakenskih senzorjev, se trenutno naslavljata z razvojem enostavnejših zasnov senzorjev in merilnih konfiguracij, ki zmanjšujejo kompleksnost in posledično ceno sistemov ob hkratnem ohranjanju zmogljivosti. V okviru doktorske disertacije so bile zasnovane in s postopki mikrostrukturiranja izdelane tri napredne optičnovlakenske senzorske strukture, ki lahko prispevajo k širitvi področja uporabe optičnovlakenskih senzorjev. Razviti so bili senzorji za kvaziporazdeljeno merjenje raztezka in temperature na kratkih območjih merjenja, električno pasivni dvoosni senzor pospeška na vrhu štirijedrnega vlakna in kompakten dvoosni senzor nagiba. Prvi senzorski sistem predstavlja kvaziporazdeljen senzor za merjenje raztezka in temperature, ki je bil realiziran z vpisom zrcal v jedro optičnega vlakna s femtosekundnim laserjem. Senzorska struktura vključuje kratko merilno območje (nekaj 10 mm), vzdolž katerega so razporejeni merilni segmenti enakih dolžin. Struktura je zasnovana tako, da omogoča enostavno spektralno razločevanje oziroma branje z uporabo telekomunikacijske DFB diode, fotodetektorja in mikrokrmilnika. Princip delovanja temelji na analizi interferenčnih vzorcev z izračunom medsebojnih faznih zamikov posameznih vzorcev za zaznavanje majhnih sprememb dolžin optičnih poti posameznih segmentov. Predstavljen senzor skupaj s cenovno učinkovitim sistemom za branje dosega ločljivosti, primerljive s sorodnimi, kompleksnejšimi izvedbami. Prav tako je bilo v okviru disertacije demonstrirano vgrajevanje senzorja v mehke materiale za potrebe taktilnih aplikacij. Naslednji, drugi, sklop doktorske raziskave je zajemal miniaturen dvoosni optičnovlakenski merilnik pospeška na osnovi štirijedrnega optičnega vlakna in vztrajnostne mase, ki je na vrh vlakna vpeta s superelastično žičko, narejeno iz zlitine nikelj-titan, medtem ko je izmik vztrajnostne mase iz ravnovesne lege odvisen od pospeška, ki deluje na njo. Izdelana struktura na vrhu štirijedrnega vlakna skupaj z vztrajnostno maso tvori štiri Fabry–Pérot interferometre, ki so nadalje uporabljeni za diferencialno, temperaturno kompenzirano merjenje premikov mase, ki jih povzroči pospešek, v dveh oseh. Razvit postopek izdelave omogoča nastavljivost senzorja v širokem razponu lastnih frekvenc ter občutljivosti. Tretji sklop raziskave se je nanašal na kompakten dvoosni optičnovlakenski inklinometer, zasnovan na osnovi vlakenskega HfO2 zrcala in štirijedrnega vlakna, na konec katerega je s palčko SiO2, premera približno 15 µm, pripeta keramična vztrajnostna masa. Odmik vztrajnostne mase iz ravnovesne lege je sorazmerno odvisen od nagiba strukture, kar omogoča neposredno razločevanje kota nagiba iz meritev odmika vztrajnostne mase iz ravnovesne lege. Vlakensko zrcalo, vrh štirijedrnega vlakna in vztrajnostna masa tvorijo skupek dvanajstih Fabry-Pérot interferometrov (skupina treh interferometrov različnih dolžin na eno jedro štirijedrnega vlakna), ki so nadalje uporabljeni za diferencialno meritev odmika mase v dveh dimenzijah in meritev spremembe temperature strukture. Doktorska disertacija predstavlja kompaktne, visokozmogljive, enostavno razločljive in električno pasivne senzorske strukture, ki so bile izdelane s posebnimi postopki mikrostrukturiranja optičnih vlaken.
Keywords:Mikrostrukturiranje, napredne senzorske strukture, senzor, optično vlakno, razločevanje, kvaziporazdeljeno merjenje, raztezek, temperatura, pospešek, naklon, Fabry-Pérot interferometer
Place of publishing:Maribor
Place of performance:Maribor
Publisher:[J. Javornik]
Year of publishing:2026
Number of pages:XV, 173 str.
PID:20.500.12556/DKUM-98095 New window
UDC:681.586.5:[666.189.21:666.22](043.3)
COBISS.SI-ID:286950915 New window
Publication date in DKUM:03.08.2026
Views:294
Downloads:39
Metadata:XML DC-XML DC-RDF
Categories:KTFMB - FERI
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Licences

License:CC BY-NC-ND 4.0, Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International
Link:http://creativecommons.org/licenses/by-nc-nd/4.0/
Description:The most restrictive Creative Commons license. This only allows people to download and share the work for no commercial gain and for no other purposes.
Licensing start date:15.05.2026

Secondary language

Language:English
Title:Microstructuring and interrogation of advanced fiber-optic sensing structures
Abstract:The field of optical fiber sensors has undergone significant development in recent decades. Fiber-optic sensors enable the measurement of physical and chemical quantities with high resolution and sensitivity, while also offering unique advantages such as immunity to electromagnetic interference, the ability to operate in harsh environments, an electrically passive structure, and the capability for straightforward implementation of distributed sensing schemes. Despite these advantages, their broader adoption across a wider range of applications is limited by the complexity and cost inefficiency of interrogation systems and sensor structures. These limitations are currently being addressed through the development of simpler sensors and measurement configurations that reduce system complexity and cost while maintaining performance. Within the scope of this thesis, three advanced optical fiber sensor structures were designed and fabricated using micro-structuring techniques, contributing to the expansion of application areas for optical fiber sensors. Sensors were developed for quasi-distributed measurement of strain and temperature over short sensing regions, an electrically passive two-axis accelerometer at the tip of a four-core fiber, and a compact two-axis inclinometer. The first sensor system is a short-range quasi-distributed sensor for measuring strain and temperature, realized by inscribing mirrors into the core of an optical fiber using a femtosecond laser. The sensing structure includes a short measurement region (~ 10 mm), along which equally long sensing segments are distributed. The structure is designed to allow simple spectral interrogation using a telecommunications DFB diode, a photodetector, and a microcontroller. Its operating principle is based on the analysis of interference patterns by calculating relative phase shifts between individual patterns to detect small changes in optical path lengths of individual segments. The presented sensor, together with a cost-effective interrogation system, achieves resolutions comparable to related but more complex implementations. Additionally, embedding of the sensor into soft materials for tactile applications was demonstrated during the dissertation. Furthermore, a high spatial resolution version was developed to demonstrate configurability, making it suitable for precision applications. The second part of the doctoral research focused on a miniature two-axis optical fiber accelerometer based on a four-core optical fiber and an inertial mass attached to the fiber tip with a superelastic nickel–titanium wire. The structure is based on an elastically suspended inertial mass, displacement of which from equilibrium depends on the exerted acceleration. The fabricated structure at the fiber tip, together with the inertial mass, forms four Fabry-Pérot interferometers, which are used for differential, temperature-compensated measurement of mass displacement caused by acceleration along two sensing axes. The developed fabrication process allows tuning of the sensor across a wide range of natural frequencies and sensitivities. The third part of the research focused on the compact two-axis optical fiber inclinometer, based on an in-fiber HfO₂ mirror and a four-core fiber. An inertial mass is attached to the end of the fiber via a SiO₂ beam with a diameter of 15 µm. The displacement of the inertial mass from its equilibrium position is proportional to the tilt of the structure, enabling tilt angle measurement. The structure at the four-core fiber tip and the inertial mass form a set of twelve Fabry-Pérot interferometers (a group of three interferometers of different lengths per core), which are used for differential measurement of mass displacement in two dimensions and for temperature sensing. The doctoral thesis presents compact, high-performance, simply interrogated, and electrically passive sensor structures fabricated using specialized fiber micro-structuring techniques.
Keywords:Microstructuring, Advanced sensing structures, sensor, optical fiber, interrogation, quasi-distributed measurement, strain, temperature, acceleration, inclination, Fabry-Pérot interferometer


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